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Accelerated Hyperspectral Unmixing With Endmember Variability Via The Sum-Product Algorithm, Charan Puladas
Accelerated Hyperspectral Unmixing With Endmember Variability Via The Sum-Product Algorithm, Charan Puladas
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The rich spectral information captured by hyperspectral sensors has given rise to a number of remote sensing applications, ranging from vegetative assessment and crop health monitoring, to military surveillance and combatant identification. However, due to limited spatial resolution, multiple ground materials generally contribute, i.e. mix, to form the spectrum recorded for a single pixel. The unmixing problem considers the inverse problem of determining the underlying material spectra, called endmembers, from sensor measurements. While classical unmixing approaches were deterministic in nature and did not attempt to identify in-scene materials, recent methods use labeled training data to generate statistical models of endmember …
Direction Of Arrival Estimation Using Wideband Spectral Subspace Projection, Majid Shaik
Direction Of Arrival Estimation Using Wideband Spectral Subspace Projection, Majid Shaik
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Many areas such as Wireless Communication, Oil Mining, Radars, Sonar, and Seismic Exploration require the direction of arrival estimation (DOA) of wideband sources. Most existing wideband DOA estimation algorithms decompose the wideband signals into several narrowband frequency bins, followed by either focusing or transforming to a reference frequency bin, before estimating the DOAs. The focusing based methods are iterative and their performance is affected by the choice of preliminary DOA estimates and the number of source DOAs to be estimated. The existing method requiring transformation to a reference frequency bin exhibits spurious peaks in the spatial spectrum and is not …
Signal Subspace Processing In The Beam Space Of A True Time Delay Beamformer Bank, Nathan Allen Wilkins
Signal Subspace Processing In The Beam Space Of A True Time Delay Beamformer Bank, Nathan Allen Wilkins
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A number of techniques for Radio Frequency (RF) source location for wide bandwidth signals have been described that utilize coherent signal subspace processing, but often suffer from limitations such as the requirement for preliminary source location estimation, the need to apply the technique iteratively, computational expense or others. This dissertation examines a method that performs subspace processing of the data from a bank of true time delay beamformers. The spatial diversity of the beamformer bank alleviates the need for a preliminary estimate while simultaneously reducing the dimensionality of subsequent signal subspace processing resulting in computational efficiency. The pointing direction of …
Adaptive Noise Reduction Techniques For Airborne Acoustic Sensors, Ryan Michael Fuller
Adaptive Noise Reduction Techniques For Airborne Acoustic Sensors, Ryan Michael Fuller
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Ground and marine based acoustic arrays are currently employed in a variety of military and civilian applications for the purpose of locating and identifying sources of interest. An airborne acoustic array could perform an identical role, while providing the ability to cover a larger area and pursue a target. In order to implement such a system, steps must be taken to attenuate environmental noise that interferes with the signal of interest. In this thesis, we discuss the noise sources present in an airborne environment, present currently available methods for mitigation of these sources, and propose the use of adaptive noise …
Detection Of Small Aircraft Using An Acoustic Array, Anne M. Zelnio
Detection Of Small Aircraft Using An Acoustic Array, Anne M. Zelnio
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Detection of small aircraft visually or with radar sensors is difficult due to its small size, low-velocity, and low radar cross section. This effort investigates the detection and localization of small aircraft using an acoustic array. The acoustic array was fabricated using low-cost commercial off-the shelf (COTS) hardware that is mobile and can adapt to different signatures and deployment environments. A cross-correlation method for calibration and delay-and-sum beamforming was performed. A generalized likelihood ratio test (GLRT)-based energy detector and a GLRT-based sinusoidal signal detector was applied after beamforming. Detection was also performed using various subpace adaptive beamforming techniques including MUSIC, …
Simultaneous Rf/Eo Tracking And Characterization Of Dismounts, Jason M. Blackaby
Simultaneous Rf/Eo Tracking And Characterization Of Dismounts, Jason M. Blackaby
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This thesis discusses the fusion of radar frequency(RF) data and electro-optical (EO) data for tracking and characterization of dismounts (i.e., humans). Each of these sensor modalities provides unique information about the location, structure, and movement of a dismount. The person's location is tracked on the 2D ground plane using RF data for range measurements and EO data for angle measurements. Using this information, measurements are made on the structure and dynamic motion (gait) of the person. An imaging approach is used to create spatio-temporal activity maps along with a three-dimensional reconstruction of the dismount.
Improved Thresholding Technique For The Monobit Receiver, Jonathan Gordon Buck
Improved Thresholding Technique For The Monobit Receiver, Jonathan Gordon Buck
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Wideband digital receivers typically use a very high sampling rate to capture a signal for near real-time processing. Very robust digital techniques, like the Monobit FFT technique, have been developed to provide near real-time processing of captured timedomain signals. Most of these techniques trade accuracy for processing speed by approximating computationally complex mathematical operations. The approximation sometimes makes it difficult to detect multiple signals if the difference between their amplitudes is more than a few dB. This thesis presents a dynamic thresholding technique for multi-tone signal detection. The technique is based on setting an allowable ratio between the magnitude of …